Due to the quantum size effect, semiconductor quantum dots (i.e. semiconductor nanocrystals of which all three dimensions are smaller than the exciton Bohr diameter of the corresponding bulk materials), especially the II-VI semiconductor quantum dots, exhibit size-dependent optical properties different from those of the corresponding bulk materials. This characteristic is useful in the preparation of light-emitting diode, solar cell single electron laser, etc. Therefore synthesis of size-controllable semiconductor quantum dots has become one of the focuses of recent research. Optical properties of semiconductor quantum dots are related to their size distribution. The narrower the size distribution, the purer the color of emission light. High purity of the light is extremely important to the practical applications of the semiconductor quantum dots. Thus, synthesis of high-quality semiconductor quantum dots with narrow size distribution is a target pursued by many scientists. In research on the synthesis of II-VI semiconductor quantum dots, the method of thermal decomposition of organometallic compound precursor developed by M. G. Bawendi's research group is one of the most commonly employed methods for synthesizing high-quality semiconductor quantum dots with narrow size distribution (Murray C. B. et al., J. Am. Chem. Soc. 1993, 115, 8706). However, the raw materials used in this kind of methods are of highly toxicity so that they will readily pollute the environment and in addition, the experimental operation is quite complicated. Thus such methods are not suitable for large-scale industrial production. For instance, dimethyl cadmium used bis trimethylsilyl as a cadmium source, (TMS)2S used as sulfur source, (TMS)2Se or selenium powder used as selenium source, (TMS)2Te or tellurium powder used as tellurium source are all highly poisonous substances; the reaction should be carried out under the conditions free from oxygen and water; nucleation and growth reactions should be carried out separately at two different temperatures above 250° C., which makes the control of the temperature difficult in large-scale production. Furthermore, in the reaction at least one reactant should be quickly injected into a high temperature hot solution in an extremely short period of time. Such operation is also difficult to be carried out in large-scale -industrial production. Later X. G. Peng's research group made an improvement to the above-mentioned experiment. However, except for replacing relatively stable cadmium oxide for dimethyl cadmium, which is easily explosive and high toxic, other experimental conditions are substantially similar. (Peng Z. A. et al., J. Am. Chem. Soc. 2001, 123, 183). Recently, X. G. Peng's research group successfully synthesized high-quality cadmium sulfide nanocrystals (Yu, W. W. et al., Angew. Chem. Int. Ed. Eng. 2002, 41, 2368). Although the raw materials used in the reaction are environment-friendly, the nucleation and growth reactions of nanocrystals still required to be carried out at relatively high and different temperatures, and the sulfur source still required to be quickly injected into hot solution with relatively high nucleation temperature. Thus, this method is still not suitable for large-scale industrial production. Therefore, development of a novel method for the preparation of high-quality cadmium sulfide quantum dots with narrow size distribution and suitable for large-scale industrial production is urgently needed.